P15-WU Zhongqing

Elasticity of hydrous wadsleyite at high pressure and temperature: constraint on water content in the transition zone

Wenzhong Wanga, Michael J. Walterb ,Ye Penga, Simon Redfernc, Zhongqing Wua

a School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China

b School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK

c Department of Earth Science, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK

The content of olivine in the upper mantle and water in transition zone, which are critical in understanding dynamic and evolution of Earth, still remains highly controversial mainly because of inevitable extrapolation of the experimental data to pressure and temperature (PT) conditions of earth’s interior in previous studies. Here we obtained the elasticity of hydrous wadsleyite at PT conditions of Earth’s interior without extrapolation based on the density functional theory. Combining with our previous theoretical results, we found that the water content of wadsleyite in MTZ can be well constrained only if the density and velocities contrasts across 410-km discontinuity are used together. These contrasts can be well matched using the transition of olivine to wadsleyite if the ∆Vp across 410-km discontinuity is ~ 3% -5%, which includes AK135 model and is within 1s limit of Shearer and Flanagan (1999)’s results. For a pyrolitic composition model with 60% olivine, the upper part of the transition zone contains ~ 0.5 wt% water.